Surely anyone who was desperate to see the musical would have gone to Edinburgh or Chichester, not really any harder to get get to than London...
I know some people who bought tickets for London that didn't got them for Edinburgh or Chichester, for various reasons, one of them being London a far better connected city with almost any airport and also a very turistic city, so you can plan not only attending the musical to also visit the city with family or friends. Yes, Edinburgh is also very turistic but not all the airports have flights to it, and some that have it, prices are not affordable.
I also know that some of those people are waiting for a London announcement to finally being able to attend the musical.